[PATCH 3/3 v2] Make "git-remote rm" delete refs acccording to fetch specs

["Shawn O. Pearce" <spearce@spearce.org>]

A remote may be configured to fetch into tracking branches that
don't match its name.  A user may have created a remote by hand
that will fetch to a different tracking branch namespace:

  [remote "alt"]
    url = git://repo.or.cz/alt-git.git
    fetch = refs/heads/*:refs/remotes/origin/*

When deleting remote alt we should clean up the refs whose names
start with "refs/remotes/origin/", even though the remote itself
was named alt by the user.

To avoid deleting refs used by another remote we only clear refs
that are unique to this remote.  This prevents `git prune rm alt`
from removing the refs used by say origin if alt was just using a
different URL for the same repository.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---

 This is a longer, but better version of this patch.  Instead of
 blindly deleting the refs we remove them only if this is the last
 remote that would write to the local tracking ref.

 builtin-remote.c |   68 ++++++++++++++++++++++++++++++++++++++++++-----------
 1 files changed, 54 insertions(+), 14 deletions(-)

diff --git a/builtin-remote.c b/builtin-remote.c
index e5cfc88..c49f00f 100644
--- a/builtin-remote.c
+++ b/builtin-remote.c
@@ -267,27 +267,65 @@ static int get_ref_states(const struct ref *ref, struct ref_states *states)
 	return 0;
 }
 
+struct known_remote {
+	struct known_remote *next;
+	struct remote *remote;
+};
+
+struct known_remotes {
+	struct remote *to_delete;
+	struct known_remote *list;
+};
+
+static int add_known_remote(struct remote *remote, void *cb_data)
+{
+	struct known_remotes *all = cb_data;
+	struct known_remote *r;
+
+	if (!strcmp(all->to_delete->name, remote->name))
+		return 0;
+
+	r = xmalloc(sizeof(*r));
+	r->remote = remote;
+	r->next = all->list;
+	all->list = r;
+	return 0;
+}
+
 struct branches_for_remote {
-	const char *prefix;
+	struct remote *remote;
 	struct path_list *branches;
+	struct known_remotes *keep;
 };
 
 static int add_branch_for_removal(const char *refname,
 	const unsigned char *sha1, int flags, void *cb_data)
 {
 	struct branches_for_remote *branches = cb_data;
+	struct refspec refspec;
+	struct path_list_item *item;
+	struct known_remote *kr;
 
-	if (!prefixcmp(refname, branches->prefix)) {
-		struct path_list_item *item;
+	memset(&refspec, 0, sizeof(refspec));
+	refspec.dst = (char *)refname;
+	if (remote_find_tracking(branches->remote, &refspec))
+		return 0;
+
+	/* don't delete a branch if another remote also uses it */
+	for (kr = branches->keep->list; kr; kr = kr->next) {
+		memset(&refspec, 0, sizeof(refspec));
+		refspec.dst = (char *)refname;
+		if (!remote_find_tracking(kr->remote, &refspec))
+			return 0;
+	}
 
-		/* make sure that symrefs are deleted */
-		if (flags & REF_ISSYMREF)
-			return unlink(git_path(refname));
+	/* make sure that symrefs are deleted */
+	if (flags & REF_ISSYMREF)
+		return unlink(git_path(refname));
 
-		item = path_list_append(refname, branches->branches);
-		item->util = xmalloc(20);
-		hashcpy(item->util, sha1);
-	}
+	item = path_list_append(refname, branches->branches);
+	item->util = xmalloc(20);
+	hashcpy(item->util, sha1);
 
 	return 0;
 }
@@ -313,8 +351,9 @@ static int rm(int argc, const char **argv)
 	};
 	struct remote *remote;
 	struct strbuf buf;
+	struct known_remotes known_remotes = { NULL, NULL };
 	struct path_list branches = { NULL, 0, 0, 1 };
-	struct branches_for_remote cb_data = { NULL, &branches };
+	struct branches_for_remote cb_data = { NULL, &branches, &known_remotes };
 	int i;
 
 	if (argc != 2)
@@ -324,6 +363,9 @@ static int rm(int argc, const char **argv)
 	if (!remote)
 		die("No such remote: %s", argv[1]);
 
+	known_remotes.to_delete = remote;
+	for_each_remote(add_known_remote, &known_remotes);
+
 	strbuf_init(&buf, 0);
 	strbuf_addf(&buf, "remote.%s", remote->name);
 	if (git_config_rename_section(buf.buf, NULL) < 1)
@@ -352,9 +394,7 @@ static int rm(int argc, const char **argv)
 	 * the branches one by one, since for_each_ref() relies on cached
 	 * refs, which are invalidated when deleting a branch.
 	 */
-	strbuf_reset(&buf);
-	strbuf_addf(&buf, "refs/remotes/%s/", remote->name);
-	cb_data.prefix = buf.buf;
+	cb_data.remote = remote;
 	i = for_each_ref(add_branch_for_removal, &cb_data);
 	strbuf_release(&buf);
 
-- 
1.5.6.rc0.158.g7c7a1